I can't be arsed to figure out which of these are "actually" indie or just seemingly lower budget, so:

• SIGNALIS - unmatched aesthetic & vibes, after finishing it the first time I kept thinking about it so went back for a second round on survivor/classic difficulty
• Pizza Tower - it's just so peak
• Nidhogg - I think this came out more than five years ago but I finally played it this year. Even though it's extremely basic and doesn't have a real campaign it's just so incredibly polished in its deceptively simple combat system that I kept coming back for more.
• Return of the Obra Dinn - spent a wonderful Sunday afternoon solving this one sitting at my kitchen table with my steam deck and giant ledger notebook
• Into the Breach - extremely fun, every single turn feels absolutely clutch; however you have to play basically perfectly in order to win so it is quite stressful
• Night in the Woods - explicitly leftist game, one of the few
• The Messenger - this one is really fun and has great music. My partner still remembers and talks about watching me play it.
• Katana Zero - it's got that one hit kill/quick retry mechanic, excellent game. It's the game that Hotline Miami wishes it was imo.
• Hyper Light Drifter - there are some massive unwarranted difficulty spikes but if you get around those this is a wonderful, beautiful game